How much energy can be harvested if solar panels are installed on the roof of a passenger car?

When German automotive startup Sono Motors unveiled a pre-production prototype of its Sion solar-electric family car, the company also showed off a giant solar-powered trailer in partnership with Finnish company Valoe as part of the 2021 CES show. Now, the idea is hitting the streets, but in the form of a specially developed passenger-carrying trailer bus.

Sono estimates that under ideal conditions, photovoltaic cells on the hood, roof, sides and back of its upcoming Sion solar electric vehicle could add as much as 245 kilometers (152 miles) of range per week to its batteries. But how much energy can be harvested if solar panels are mounted on the roof of a passenger car? Sono has teamed up with Munich-based MVG to find answers.

Around 20 semi-flexible photovoltaic modules have been mounted on the roof of a bus trailer that will be driven on the roads of downtown Munich, following a passenger bus operated by the local transport company Münchner Verkehrsgesellschaft (MVG) for testing real-world energy production and measure the technology's potential in everyday use.

This is a milestone in Sono Motors' mission to make every vehicle solar. Especially at a time of rising energy prices and increasing emissions regulations in urban areas, solar technology offers enormous added value to public transport operators. City buses and coaches, whether electric or diesel powered, have plenty of room and are on the road every day. MVG's first solar-powered bus trailer will roll into the streets of Munich in the future, allowing MVG's passengers to experience solar-powered transportation in everyday use.

Sono estimates that this technology has the potential to save 2,500 liters (550 gallons) of diesel per bus per year and 6.5 tons of CO2 emissions, meaning an operator running a modest fleet of 300 buses could potentially Up to 2,000 metric tons of carbon dioxide emissions will be reduced.